The (Greek, Ancient (to 1453);: Ἑταιρεία|Hetaireía, pronounced as /grc/, Latinized as Latin: hetaeria) was a term for a corps of bodyguards during the Byzantine Empire.
means (from Greek, Ancient (to 1453);: {{Wikt-lang|grc|ἑταῖρος|ἑταῖροι), echoing the ancient Macedonian Companions and the Classical Greek aristocrats who attended .[1]
The most important such corps was the 'Imperial ' (Greek, Ancient (to 1453);: βασιλική ἑταιρεία,), composed chiefly of foreigners, which formed part of the Byzantine professional standing army alongside the in the 9th–12th centuries. The term was also applied to the smaller bodyguards of thematic military commanders, headed by a count (Greek, Ancient (to 1453);: κόμης τῆς ἑταιρείας,), and from the 13th century on, it was employed in a generic sense for the armed retinues of magnates, bound by oath to their master.
The exact origin, role, and structure of the Imperial are unclear. The term first appears in the early 9th century, as the bodyguard of Emperor Leo V the Armenian on campaign. It is unclear, however, whether the usage is technical, referring to a specific unit, or simply as a term for bodyguard; it is not until the reign of Theophilos that the unit is definitely attested. John B. Bury theorized that it was the evolution of the earlier Latin: [[Foederati]], but this supposition was rejected by John Haldon as the two units are mentioned as co-existing in some sources. According to Haldon, it likely began as part of the of the —which also functioned as a palace guard in its early history—before becoming an independent unit.
The bulk of the was apparently composed of foreigners, and contemporary accounts list Khazars,, (i.e. Magyars), Franks and Arabs. Hans-Joachim Kühn even refers to it as a "Byzantine Foreign Legion". For this reason, although it is frequently mentioned alongside the native Byzantine, it was always a unit apart, with its own peculiar internal structure and a different role: whereas the were the professional regiments forming the core of the Byzantine army on campaign, the was responsible for the protection of the emperor's person.
The of the 9th–10th centuries was divided in several units: three or four according to the sources, distinguished by their epithets and each, at least originally, under is respective (Greek, Ancient (to 1453);: ἑταιρειάρχης|master of the ''hetaireia'').
The senior unit was the 'Great ' (Greek, Ancient (to 1453);: μεγάλη ἑταιρεία,), under the, who ranked as the senior of the military officials known as and was often referred to simply as 'the ' (Greek, Ancient (to 1453);: ὁ ἑταιρειάρχης) par excellence. It was a very important position in the late 9th and first half of the 10th centuries, as he was in charge of the emperor's security, and was entrusted with delicate assignments. It is telling that the future emperor Romanos Lekapenos held this post, and was succeeded by his son Christopher Lekapenos. According to the mid-10th century De Ceremoniis, written by Emperor Constantine VII Porphyrogennetos, the and his unit are charged with the protection of the emperor's tent on campaign, and with the security of the imperial palace, in close association with another palace official, the .
A 'Middle ' (Greek, Ancient (to 1453);: μέση ἑταιρεία,) is attested in sources, and the possible existence of a 'Lesser ' (Greek, Ancient (to 1453);: μικρὰ ἑταιρεία,) is implied by the reference to Stylianos Zaoutzes as under Emperor Michael III . Alternatively, the unit of the may be identical to the barbarian regiment composed of the two companies of the (Greek, Ancient (to 1453);: Χαζάροι, Khazars) and the, which is called the 'Third ' (Greek, Ancient (to 1453);: τρίτη ἑταιρεία,) in the Escorial Taktikon of . The historian Warren Treadgold estimates the total strength of the Imperial in the early 10th century at 1,200 men.
By the early 10th century, honorary posts in the were prestigious appointments that could be purchased by native Byzantine officials, connected to an annual stipend paid by the imperial treasury to the holder. A post in the 'Great ' cost a minimum of 16 of gold and paid a of 40, with one additional for each additional seven ; a post in the 'Middle ' a minimum of ten, with a of 20 ; and in each of the or companies, a minimum of seven, with a of 12 . According to Haldon, this may be evidence that the "was developing already into a show force, and eventually no longer served as a fighting part of the imperial guard".
As the 10th century progressed, a tendency of amalgamation of the various units into a single command becomes evident, as the 'Middle ' seems to have been placed under the . The importance of the as a bodyguard corps declined thereafter, but the unit was one of the few regiments of the middle Byzantine army to survive into the Komnenian-era army, being attested well into the reign of Emperor Manuel I Komnenos . By this time, however, its composition had changed: in the late 11th century, Nikephoros Bryennios the Younger reports that the was "customarily" made up of young Byzantine nobles rather than foreigners.
The post of also survived, and, detached from its military duties, remained an important court position: it was held by several influential palace eunuchs in the 11th century, and by second-rank nobles and junior relatives of the Byzantine imperial family, such as George Palaiologos, in the Komnenian period. In the Palaiologan period, it was held by members of prominent noble families.